Unable to customize strip in facet_grid

Question

I am trying to customize the strip in facet_grid function. My graph currently looks like:

I successfully changed the background of strip to purple, however, I could not change the border color to black, even though I set the color to 'black' in the function.

Also, I want the space between text and the rectangle to be larger so that it will looks nicer. How should I achieve this?

My codes looks like:

plot.density <- ggplot(df_densityWindow, aes(x = idx, y = density,     color = factor(location))) + 
geom_bar(stat = 'identity', fill = 'white') + 
facet_grid(marker ~ case, scales = 'free') +
theme(strip.background = element_rect(colour="red", fill="#CCCCFF")) +
scale_color_manual(name = 'Regions',values = c("#F26969", "#02f527",'#F2F2C6')) +
background_grid(major = 'y', minor = "none") + # add thin horizontal lines 
xlab('Index') +
ylab(expression(paste('Density/', mm^2, ))) +
theme(axis.title = element_text(size = 28)) +
theme(axis.text = element_text(size = 26)) +
theme(legend.text = element_text(size = 16)) +
theme(legend.title = element_text(size = 18)) +
panel_border() # and a border around each panel
plot(plot.density)

If necessary, the data could be downloaded here: data Thank you!

Answer 1

Your colour specification for strips works without error for me. The spacing between the strip text and box can be increased by setting the margin argument at the strip.text theme:

ggplot(iris, aes(Sepal.Width, Sepal.Length)) +
  geom_point() +
  facet_grid(Species ~ rev(Species)) +
  theme(strip.background = element_rect(colour="red", fill="#CCCCFF"),
        strip.text = element_text(margin = margin(10, 10, 10, 10)))

Possible debug strategy:

1. Reproduce code above

1A. If that doesn't work, check if your ggplot versions is ~3.2-ish

1B. If that does work, proceed to 2.

2. Try to remove and place back lines of plotting to see where the error occurs

I'm particularly unfamiliar with panel_border() and background_grid(), so you could try those first.

EDIT: Plot based on data and code provided

ggplot(data, aes(x = idx, y = density, colour = factor(location))) +
  geom_col(fill = "white") +
  scale_color_manual(name = 'Regions',values = c("#F26969", "#02f527",'#F2F2C6')) +
  facet_grid(marker ~ case, scales = "free") +
  xlab('Index') + 
  ylab(expression(paste('Density/', mm^2, ))) +
  theme(strip.background = element_rect(colour = "red", fill = "#CCCCFF"),
        strip.text = element_text(margin = margin(10, 10, 10, 10)),
        axis.title = element_text(size = 28),
        axis.text  = element_text(size = 26),
        legend.text = element_text(size = 16),
        legend.title = element_text(size = 18),
        # Improvised based on missing functions
        panel.grid.major.x = element_blank(),
        panel.grid.major.y = element_line(colour = "grey90"),
        panel.background = element_rect(fill = "white", colour = NA),
        panel.border = element_rect(colour = "grey90", fill = NA))